Stars Steppin' Out

The New York City Police Department estimated that 18,000 Directioners were packed into about two blocks outside a temporarily renamed Studio 1D.

The band also discussed the upcoming documentary about them, "One Direction: This Is Us," which is hitting theaters Aug. 29 and Aug. 30, and why they decided to let 11 cameras follow their every move for a year.

"There's only so much you can get across on social media or in a five minute interview," Niall Horan told the "Today." "So we really wanted to give behind-the-scenes access."

"It's also about our families as well, the way they deal with us being away from home," Liam Payne added.

Fans, some of whom lined up a week ago, took to social media to share their excitement about seeing the band live as part of the Toyota Summer Concert Series.